Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:4.6.1.1 (adenylate cyclase)
 19,190 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. Adenylate cyclase (EC 4.6.1.1) activity was characterized in human liver, and its subcellular distribution compared with that of three other potential enzyme markers of the pericellular membrane: leucine aminopeptidase (EC 3.4.11.1), gamma-glutamyltransferase (EC 2.3.2.2) and 5'-nucleotidase (EC 3.1.3.5). Although these three enzyme activities were detected in each of the subcellular fractions studied, 85% of the total adenylate cyclase activity was found in the 1000 g pellet ('nuclear' fraction) with a threefold increase in specific activity as compared with the homogenate. No adenylate cyclase activity existed in the 150 000 g supernatant fraction. 2. In the 'nuclear' fraction, adenylate cyclase activity was increased in a dose-dependent fashion by glucagon with a half-maximal stimulation at 10 nmol/l and a maximal four- to seven-fold increase at 1 mumol/l. Catecholamines activated adenylate cyclase 2.5- to three-fold, with an order of potency (protokylol greater than isoprenaline greater than adrenaline greater than noradrenaline) typical of a beta 2-adrenoreceptor. Prostaglandin E1 and NaF also stimulated cyclase two- and four-fold respectively. Insulin, serotonin, dopamine, thyroid-stimulating hormone and ACTH had no effect. Adenosine provoked a weak inhibition at 0.1 mmol/l. Finally guanosine triphosphate and 5'-guanylyl imidodiphosphate induced a marked increase in basal activity, four- and eight-fold respectively, but both reduced the relative increase in enzyme activity due to glucagon or adrenaline. 3. Cyclase from foetal liver (12--16 weeks old) and cirrhotic adult liver appeared to behave similarly to that from normal liver; however, foetal cyclase was more active, and cirrhotic enzyme less active than normal adult liver. Both systems responded to catecholamines via a beta 2-adrenoreceptor. 4. These results validate the use of rat liver adenylate cyclase as a tool for pharmacological and physiological studies.
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PMID:The adenylate cyclase system in human liver: characterization, subcellular distribution and hormonal sensitivity in normal or cirrhotic adult, and in foetal liver. 4 65

Changes in activities of plasma membrane enzymes during liver regeneration may be related to the maintenance of hepatic function or to the regulation of cell proliferation. Plasma membranes were isolated from rat livers at various times after partial hepatectomy, and the specific activities of alkaline phosphatase, (Na+ + K+)-ATPase, leucine aminopeptidase, 5'-nucleotidase, and adenylate cyclase (basal and with glucagon or epinephrine) were measured. Alkaline phosphatase and (Na+ + K+)-ATPase activity increased 3.6-fold and 2-fold respectively, during the first 48 h after partial hepatectomy. The time of onset and duration of change suggest that these increases in activity are involved in the maintenance of bile secretion. Decreases in leucine aminopeptidase activity at 48--108 h and in 5'-nucleotidase activity at 12--24 h were observed, which may be involved in the restoration of protein and accumulation of RNA. The basal activity of adenylate cyclase increased after partial hepatectomy. The response of adenylate cyclase to epinephrine showed a transitory increase between 36 and 108 h after surgery, while the response to glucagon was decreased by approximately 50% at all time points through 324 h after surgery. These changes in the hormone responsiveness of adenylate cyclase are similar to those previously observed in fetal and preneoplastic liver.
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PMID:Changes in plasma membrane enzyme activities during liver regeneration in the rat. 14 24

We have perfused isolated rat livers with hypocalcemic (4.4 mg 100 ml) Krebs-Ringer bicarbonate albumin buffer. After 15 min of perfusion, a substance appeared in the perfusate which decreased rat renal adenylate cyclase activation by parathyroid hormone (PTH). The material in the perfusate was purified greater than 50,000-fold by Bio-Gel P-10 chromatography. The purified antagonist decreased the activation of rat renal cortical adenylate cyclase by PTH, glucagon, and epinephrine 75 to 100%. Concentration response curves for each of the hormones indicated a noncompetitive interaction of the inhibitor with the hormone. The inhibition was not species-specific, as the activation of the parathyroid hormone-responsive adenylate cyclase in cat renal cortex was also abolished by the inhibitor from the perfused rat liver. The inhibitor is a peptide, Mr equal to similar to 1000, which is heat-stable, acid-stable, alkai-labile, and is destroyed by trypsin, leucine aminopeptidase, and elastase. It is not destroyed by phosphodiesterase, 5'-nucleotidase, alkaline phosphatase, neuraminidase, RNase, or phospholipase A. The inhibitor is not produced by isolated rat livers perfused with normocalcemic perfusion media. It is unclear whether the peptide is synthesized by the liver or whether it is a breakdown product of a larger peptide or protein in the liver. This is the first reported peptide inhibitor of adenylate cyclase.
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PMID:Isolation of a unique peptide inhibitor of hormone-responsive adenylate cyclase. 16 24

The possible role of cytoplasmic microtubules in the renal handling of phosphate and its regulation by parathyroid hormone (PTH) was evaluated with colchicine, a microtubule-disrupting agent. Colchicine-treated rats were thyroparathyroidectomized (TPTX) and subsequently infused with PTH. Treatment with a total dose of 1 mg colchicine had no effect on glomerular filtration rate or fractional excretions of sodium and potassium. Fractional excretion of phosphate in colchicine-treated TPTX rats was significantly higher compared with TPTX controls. After PTH infusion, control rats responded with increases in fractional excretion of phosphate and urinary cyclic AMP but colchicine-treated rats had variable and insignificant changes in both parameters. Fractional excretion of sodium and potassium did not change significantly after PTH. Renal cortical activities of cyclic AMP phosphodiesterase, soluble alkaline phosphatase, cytochrome oxidase, leucine aminopeptidase, or basal adenylate cyclase were not significantly affected by colchicine treatment. On the other hand, stimulation of adenylate cyclase by a submaximal dose of PTH was markedly decreased in colchicine-treated rats, and the activity of membrane-bound alkaline phosphatase was also significantly decreased. The binding of radioactive colchicine in renal cortical extracts from rats treated with colchicine was significantly diminished. These results suggest that disruption of cytoplasmic microtubules in renal cortical cells interferes with phosphate transport and its regulation by PTH.
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PMID:Effect of colchicine on urinary phosphate and regulation by parathyroid hormone. 18 12

Total renal ischemia for various time intervals (0-50 min) resulted in the rapid and duration-dependent redistribution of polarized membrane lipids and proteins in renal proximal tubule cells. Following only 15 min of ischemia, apical membrane enrichment of NaK-ATPase, normally a basolateral membrane (BLM) enzyme, had increased (1.6 +/- 0.6 vs. 2.9 +/- 1.2, P less than 0.01). In vivo histochemical localization of NaK-ATPase showed reaction product throughout the apical microvillar region. PTH-stimulatable adenylate cyclase, another BLM protein, was also found in ischemic but not control apical membrane fractions. One dimensional SDS-PAGE showed four bands, present in control BLM and ischemic apical membranes, which could not be found in control apical membrane fractions. Immunohistochemical localization of leucine aminopeptidase (LAP) showed the enzyme was limited to the apical domain in control cells. Following ischemic injury (50 min), LAP staining could be seen within the cell and along the BLM. Following 24 hr of reperfusion, the BLM distribution of LAP was further enhanced. With cellular recovery from ischemic injury (5 days), LAP was again only visualized in the apical membrane. Duration-dependent alterations in apical and BLM lipids were also observed. Apical sphingomyelin and phosphatidylserine and the cholesterol-to-phospholipid ratio decreased rapidly while apical phosphatidylcholine and phosphatidylinositol increased. Taken together, these results indicate renal ischemia causes rapid duration-dependent reversible loss of surface membrane polarity in proximal tubule cells.
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PMID:Characterization of ischemia-induced loss of epithelial polarity. 246 76

High voltage free flow electrophoresis has been applied to the separation of human platelet membranes. After short treatment with neuraminidase at the whole cell level, three membrane vesicle subpopulations have been isolated. Using a surface label (125I-labeled Lens culinaris lectin), the marker enzyme NADH-cytochrome c reductase, and lipid analysis, two of the fractions have been identified as of surface origin and the other consists of intracellular membrane elements. The distribution of adenylate cyclase, leucyl aminopeptidase, 5'-nucleotidase and Ca2+-ATPase has also been investigated, and their usefulness as markers for the different membrane fractions has been evaluated. All three fractions are vesicular but differ in size and character. Their phospholipid and cholesterol contents have been determined, and the cholesterol/phospholipid ratios of the two surface fractions are over twice that of the intracellular membrane, which also has a significantly lower microviscosity as determined by fluorescence polarization using diphenyl hexatriene. The polypeptide profiles from sodium dodecyl sulfate-polyacrylamide gel electrophoresis are particularly distinctive, with actin present in the two surface membrane fractions and absent from the intracellular membranes. Myosin, confirmed by its ATPase characteristics, is almost exclusively localized in one of the surface membrane fractions, and actin-binding protein is a prominent feature of the other.
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PMID:Characterization of human platelet surface and intracellular membranes isolated by free flow electrophoresis. 626 Jul 85

Studies assessing mechanisms of proximal tubular cell (PTC) physiology and pathophysiology increasingly utilize cell culture systems to avoid the complexity of whole organ/whole animal experiments. However, no well-differentiated PTC line derived from adult human kidney currently exists. Therefore, the goal of this research was to establish such a line by transduction with human papilloma virus (HPV 16) E6/E7 genes. A primary PTC culture from normal adult human renal cortex was exposed to a recombinant retrovirus containing the HPV 16 E6/E7 genes, resulting in a cell line designated HK-2 (human kidney-2) which has grown continuously in serum free media for more than one year. HK-2 cell growth is epidermal growth factor dependent and the cells retain a phenotype indicative of well-differentiated PTCs (positive for alkaline phosphatase, gamma glutamyltranspeptidase, leucine aminopeptidase, acid phosphatase, cytokeratin, alpha 3 beta 1 integrin, fibronectin; negative for factor VIII-related antigen, 6.19 antigen and CALLA endopeptidase). Furthermore, HK-2 cells retain functional characteristics of proximal tubular epithelium (Na+ dependent/phlorizin sensitive sugar transport; adenylate cyclase responsiveness to parathyroid, but not to antidiuretic, hormone). The E6/E7 genes are present in the HK-2 genome, as determined by PCR. To assess its potential usefulness as a tool for studying injury and repair, HK-2 cells were exposed to a toxic concentration of H2O2 +/- iron chelation (deferoxamine) or hydroxyl radical scavenger (Na benzoate) therapy. Only the former blocked H2O2 cytotoxicity, reproducing results previously obtained with freshly isolated rat proximal tubular segments. In conclusion, an immortalized adult human PTC line has been established by transduction with HPV 16 E6/E7 genes. It appears to be well-differentiated on the basis of its histochemical, immune cytochemical, and functional characteristics, and it can reproduce experimental results obtained with freshly isolated PTCs. Thus, this new PTC line could have substantial research application.
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PMID:HK-2: an immortalized proximal tubule epithelial cell line from normal adult human kidney. 812 21

The effect of acute whole body exposure to ionizing radiation was investigated on intestinal vasoactive intestinal peptide (VIP) receptors and adenylate cyclase activity in membranes isolated from pig jejunum. Pigs under light anaesthesia were exposed to a single dose (6 Gy) of gamma (gamma) or to mixed neutron/gamma field (ratio 1:1; neutron/gamma) irradiation. Seven days after irradiation, plasma-membranes were prepared from post mortem jejunal mucosal scrapings. Marker enzyme activities (sucrase, leucine aminopeptidase (LAP), Na,K-ATPase) were measured in each preparation. The characteristics (KD, Bmax) of VIP receptors were determined using 125I-labelled VIP. In addition VIP-sensitive adenylate cyclase activity was measured. Results showed that enzyme activities were reduced following both gamma (sucrase 67%; LAP 53%; Na/K-ATPase 29%; N = 7) and neutron/gamma (sucrase 53%; LAP 59%; Na/K-ATPase 68%; N = 5) compared with control values (N = 5). VIP receptor affinity was decreased following either type of irradiation (gamma or neutron/gamma P < 0.01) and receptor numbers increased. Both VIP- and forskolin-stimulated adenylate cyclase activities were reduced but the sensitivity of the enzyme remained the same for VIP (EC50 values (nmol dm-3)-control-1.27 +/- 0.35; gamma-2.18 +/- 0.41; neutron/gamma-1.91 +/- 0.28). In conclusion, exposure to either gamma or neutron/gamma irradiation attenuates intestinal enzyme activities and VIP receptor affinity but increases VIP receptor numbers.
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PMID:Exposure to either gamma or a mixed neutron/gamma field irradiation modifies vasoactive intestinal peptide receptor characteristics in membranes isolated from pig jejunum. 880 Feb 7

1. Mice were subjected to gastrectomy (GX) or food deprivation (24 h). The release of insulin and glucagon in response to different secretagogues was monitored in vivo and in isolated islets 3-4 weeks after surgery. 2. GX animals responded to glucose with an impaired glucose tolerance and a poor increase in plasma insulin. Islets from GX or food-deprived mice displayed impaired insulin release to high glucose and enhanced glucagon release at low glucose. 3. After GX the insulinogenic index, Delta insulin (microU ml-1)/Delta glucose (mg ml-1), was suppressed by 65% after oral glucose and by 59% after i.v. glucose. The integrated insulin response after oral glucose was reduced by 90% in GX mice. After i.v. glucose the reduction was 67%. 4. Carbachol-induced insulin release in vivo was reduced after food deprivation and exaggerated after GX. Carbachol-stimulated glucagon secretion was suppressed after GX and after food deprivation. A similar pattern was found in vitro. 5. Cyclic AMP activation (by the phosphodiesterase inhibitor isobutylmethylxanthine or the adenylate cyclase stimulator forskolin) induced a greater insulin response in GX or food-deprived mice than in sham-operated, fed mice. A similar pattern was found in vitro. The glucagon response was enhanced in vitro but not in vivo. 6. Crude extracts of rat oxyntic mucosa enhanced basal as well as glucose-induced insulin release from isolated islets, whereas glucagon release was markedly inhibited. The effects were dose dependent, the inhibition of glucagon release being achieved at lower concentrations than the potentiation of glucose-induced insulin release. The active principle was inactivated by incubation with trypsin or leucine aminopeptidase. 7. The data suggest that a circulating agent, probably a peptide, from gastric oxyntic mucosa stimulates glucose-induced insulin secretion. It also suppresses glucagon secretion. The GX-evoked impairment of the insulin (and glucagon) response to glucose is partly compensated for by an enhanced insulin response to cholinergic and/or cyclic AMP activation.
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PMID:Gastrectomy induces impaired insulin and glucagon secretion: evidence for a gastro-insular axis in mice. 985 37

The human ileocaecal adenocarcinoma cell line HCT-8 was characterized for its potential as an in vitro organ-specific model for gastro-intestinal toxicity. HCT-8 cells showed typical epithelial cell morphology, with microvilli and intercellular junctional complexes, and formed domes, consistent with transepithelial fluid secretion. The cells express three intestinal brush-border enzyme activities (alkaline phosphatase, leucine aminopeptidase and alpha-glucosidase), and adenylate cyclase can be stimulated with vasoactive intestinal peptide. The toxicity of eight non-steroidal anti-inflammatory drugs (NSAID; indomethacin, mefenamic acid, ketoprofen, ibuprofen, sulindac, aspirin, phenylbutazone and naproxen) were assessed using the MTT and neutral red uptake assays. The MTT assay was consistently a more sensitive measure of NSAID-induced toxicity, which suggests that perturbation of mitochondrial function may be an early event in NSAID-induced cellular damage. Comparing the rankings observed in acute studies in the rat in vivo with those observed with HCT-8 cells, there are some general agreements. Indomethacin, a potent ulcerogen in vivo, was consistently among the most toxic in vitro, while aspirin and phenylbutazone have comparatively low rankings in vitro and in vivo. In man, with chronic administration, indomethacin is again ranked as a potent ulcerogen, as is aspirin, in contrast to the in vitro data with HCT-8. Therefore, NSAID-induced toxicity in HCT-8 cells assessed by the MTT or neutral red assays, can only partially predict toxicity in vivo, which suggests that local gastro-intestinal environmental factors, such as luminal acidity, may play a role in vivo. The ability of HCT-8 cells to reconstitute intact epithelial layers, thereby allowing such environmental factors to be mimicked, allows further development of these cells as a model for the in vitro prediction of in vivo gastro-intestinal toxicity.
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PMID:Toxic effects of non-steroidal anti-inflammatory drugs in a human intestinal epithelial cell line (HCT-8), as assessed by the MTT and neutral red assays. 2073 14


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